Hybrid drives already passe, as SSD sales skyrocket

Hybrid drives, which combine NAND flash with spinning disk, may still be a nascent technology, but their lifespan could be cut short by a lack of interest from consumers and computer manufacturers.

A new report from IHS iSuppli shows that while sales of hybrid drives are expected to double over the next year, that increase is unremarkable compared with sales of pure solid-state drives (SSDs), which are expected to skyrocket 2,660%.

Hybird, SSD and Cache SSD sales (Graphic: IHS iSuppli)

Hybrid hard disk drives, which contain NAND flash memory for boosting the performance of OSes and key applications, do offer an advantage over pure hard drives and are increasingly popular in ultrabooks, but cache solid state drives (SSD) will remain the mainstream ultrabook storage solution, according IHS iSuppli.

Pure SSDs are currently the leading storage type in ultrabooks, but low-capacity (20GB to 40GB) cache SSDs, which run along side hard drives in notebooks, will see shipments rise even more this year to 23.9 million units, up an astounding 2,660% from just 864,000 units in 2011. Shipments will then jump to 67.7 million units next year, cross the hundred-million-unit mark in 2015, and hit 163 million units by 2016, according to IHS iSuppli.

An example of a cache SSD is the Intel 313 series, which comes in 20GB and 24GB capacities. A cache SSD is specifically used for boosting OS and application load times.

Higher capacity, pure SSDs (with 80GB to 512GB capacity) will reach 18 million units shipped this year and 69 million by 2016.

One factor behind SSD growth: Apple, which this week again pushed the SSD envelope, releasing a version of its MacBook Pro that only contains an SSD and no hard drive. Apple is the world's leading consumer of flash memory.

Apple currently uses NAND flash in its iPad, iPod, iPhone, MacBook Air and MacBook Pro lines.

In comparison to SSD shipments, hybrid drive shipments will reach just two million units this year, up from 1 million units in 2011. IHS iSuppli predicts hybrid drive shipments will reach 25 million units by 2016.

Hard drive sales still dwarf the sales of both hybrid drives and SSDs. Hard drive shipments rose by 18% to 145 million in the first quarter of this year compared to the prior quarter, and by another 10% to 159 million in the second quarter, according to IHS iSuppli.

Currently, the only company selling hybrid drives is Seagate. The company's Momentus XT hybrid drive has up to 8GB of single-level-cell (SLC) NAND flash and 750GB of capacity on two 2.5-in hard drive platters.

Seagate struggled with the first two iterations of its Momentus hybrid drive because they contained too little flash and ran into software issues. The first drive, the Momentus 5400 PSD, had only 256MB of flash. The second hybrid drive, the Momentus XT, bumped the flash memory to 4GB and added 32MB of DDR3 cache memory.

The Momentus drives have software that learns user patterns and uses the SSD as a cache to boost performance of frequently used applications.

Western Digital Corp. and Toshiba Corp. are considering hybrid drives of their own, with models containing 8GB or more of NAND cache. Last year, SSD maker OCZ introduced its RevoDrive hybrid drive, but it came in a PCIe card form factor -- unusable in a laptop. The RevoDrive is targeted for use in workstations and for people working with high-bandwidth applications like video production, as well as gamers who love the performance that a high-end, high-priced desktop system offers.

In contrast to hybrid HDDs, cache SSDs are employed as a discrete, separate memory component alongside a hard disk drive, with both elements existing side by side, not together in one housing unit.

A sample cache SSD configuration from Acer's Aspire S3 ultrabook married a 20GB SSD to 320GB of hard disk space.

"The cache SSD solution was first hit upon by PC manufacturers because the use of a dedicated solid-state drive proved too expensive when passed on to consumers in the retail market," said IHS iSuppli analyst Ryan Chien, analyst for memory & storage at IHS. "However, a combined physical hard disk drive with a smaller cache component allowed PC makers to reap the advantages of faster responsiveness and larger capacities while keeping costs down."

For example, an Intel 320 series SSD with 160GB capacity costs from $273 to $366 on sites such as Pricegrabber.com. A Momentus XT with 500GB of capacity costs $89.00 on those sites.

While hybrid drives offer a huge cost and capacity advantage over pure SSDs, and have only slightly lower performance, they still suffer from issues surrounding mechanics and mobility. A hybrid drive inside a dropped ultrabook could be damaged beyond repair, while an SSD has no moving parts that can break.

John Rydning, IDC's research vice president for hard disk drives, said hybrid drives will not really catch on with computer manufacturers until there are more suppliers and more variety of hardware. For example, the Momentus XT hybrid drive is based on 2.5-inch form factor drives with standard 9.5mm height. In order to fit in future ultrabooks, Seagate and other manufacturers must create hybrid drives with 7mm and even 5mm z-heights, Rydning said.

"The other part of it is there's probably more than can be done to improve system performance with hybrid technology; I'd say they have not had a lot of [computer manufacturer] design wins," Rydning said, referring to manufacturers who buy the drives wholesale from Seagate.

"Seagate has done OK selling them in the aftermarket. In a sense, that's allowed them introduce them to the market and it's allowed Seagate to learn as well."

Rydning sees a healthy market for hybrid drives because PC market dynamics dictate improvements in performance and price, which hybrid drives offer. SSDs remain too expensive for most manufacturers to include in their systems.

IHS iSuppli analyst Fang Zhang agreed. He said most consumers purchasing a $700 PC or laptop aren't going to spend hundreds of dollars on an SSD. So SSDs will continue to be reserved to a niche market of high-end applications and users.

"SSDs are still way too expensive," she said. "They're at least 10X what hard drives cost."

According to iSuppli, cache SSDs, however, offer more advantages than hybrid HDDs. For instance, discrete cache SSDs and hard disk drives are much more scalable and efficient for mainstream storage, given the broad selection of drive manufacturers. And because SSDs and HDDs have lately been focused on more mobile sizes, few changes are needed for cache SSDs or thin HDDs to keep their manufacturing processes cost effective.

Additionally, the expected evolution of cache SSDs to a swappable mSATA form factor not only helps narrow the convenience advantage currently enjoyed by hybrid HDDs but also allows them to be upgraded like DRAM modules or USB drives.

HDDs sized 7mm are available with 500GB in 2.5-inch platters, with a 5-mm z-height as the next step, while hybrid HDDs are still 9-mm high. SATA SSDs are also getting denser, and NAND on the motherboard is becoming more feasible, iSuppli said in its report.

"Cost concerns, longer design cycles and tighter engineering tolerances in the case of hybrid HDDs also add to their difficulty of use in ultrabooks," iSuppli stated.

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